The Milan exchange. (Milan, Gibson County, Tenn.) 1874-1978, 1887-05-14
THE SOULS WINDOW.
Something About the Wonders
and Beauties Of the Eye.
mals-The Birds Third Eyelid-UnIOn of
the Simple and Compound in Insects.

Amidst all the marvels which the
world of nature offers to the reflective
and observant mind, there are few
which surpass in interest the wonders
revealed by study of the mechanism
of sight in the animal kingdom. An
exhaustive study of comparative anat-
Ony is by no means necessary to real
ize these wonders; in fact, we require
to be reflective as regards obvious and
familiar details, rather than learned in
scientific terms and anatomical discov-
cries No very extensive knowledge
of the structure of the eye, for instance,
is necessary to grasp the full signit-
canoe of the fact that the views obtain
able from the top of st. Paul's Cathe-
dral or the dizzy pinnacles of the Alps
enter the eye through an aperture of
about an eigth of an inch diameter,
and are reproduced in the interior of
the eye on a surface averaging the size
of sixpence, from which the size,
shape, color, position, and general
popularity of every object within range
are accurately conveyed to the brain.
This is only one of the ordinary Won
ders of the human eye, but shares the
fate of many others in that it seldom
occupies moment s thought-no more
thought, in fact, than we bestow upon
the varieties of sight in the lower ami
mails and the lessons we may learn
from them.
Most of us, in these days of cheap
science manuals, are familiar with the
general structure of our own eyes and
the rudimentary principles of optical
science; and we are so accustomed to
look upon this particular plan of con-
struction as the only one by which
vision can be accomplished, that it is
impossible not to feel astonished when
observation discloses the extraordinary
variety of structural arrangement;
which are to be found in the descend
ing scale of animals. In completely
and minuteness of detail, the eye o.
man aud the higher animals surpasse!
all others; yet its structure may be sale
80 explain itself, and to be compare
tively simple plan, when regarded il
connection with the laws of optics. /
is exactly such as might be imagined
ms consequence of known laws O
Eight transmission and known proper
ties of matter A first glimpse, there
fore, into the structure of the eyes o
the lower or invertebrate animals i
somewhat perplexing, owing to the ap
parent contradictions met with; for tn,
seemingly simple plan of the mamma
eye is lost in a diversity of externa
form and internal structure which i
truly marvellous; in some cases, tn,
elements considered to be essential ar
apparently missing; and in others, ad
ditions are found which have no coun
terpart in eyes supposed to be NOR
perfect.
A little reflection will, however, shov
that these diversities of structure
wherever met with, are necessary {,
the particular mode of life which thei
possessor was designed to lead in tn
ranks of creation. In almost all nam
mails for instance, below the Primates
third eyelid-or, as it is caAd, tn
"nictitating" membrane is found
commodiously folded up in the inne
corner of the eyeball, ready at any in
slant to sweep across its surface. Thi
is found in the eyes of all birds, and o
such quadruples as require it, its us
being to wash the eye free from an